This invention relates to paper coating additives and more particularly to a dispersion system for use as a lubricant additive.
Paper coatings are generally made from pigments, adhesives, and various additives employed for a variety of purposes. The pigment material usually comprises clay, while starch or protein is employed as the adhesive. Additives employed during the preparation of the paper coating, or at a later stage during the coating operation, include defoamers, lubricants, plasticizers, and other special property-producing chemicals.
This invention is generally concerned with paper coating additives employed as lubricants. Although a lubricant additive is primarily used to impart lubricity to the coatings, the additive also imparts plasticity to the color both in the wet an dry states, can modify the rheological properties, and can improve the gloss and ink receptivity of the finish coating. It has been generally stated that the ideal lubricant should lubricate the coating and improve its flow properties, should ensure a smoother coating, should improve the finish, should enhance th printing qualities, should reduce the tendency of the coating to crack or peel when the paper is folded, and should aid in the production process by decreasing or eliminating dusting and improve the paper finish without additional operations.
For many years, metallic soap dispersions, such as calcium stearate, have been used as a lubricant for pigmented paper coatings. Although many products have been tried as substitutes for calcium stearate, none have been totally successful. Although calcium stearate is an effective lubricant, a less expensive additive which imparts improved qualities to the paper coating has long been sought.
Therefore, it is a principal object of this invention to provide a paper coating additive for use as a lubricant having improved viscosity effects on the coating as compared to those normally found in prior art paper coating lubricants.
Another object of this invention is to provide a paper coating additive of the above character imparting a greater degree of gloss and brightness to paper coatings than those found in the prior art.
Another object of this invention is to provide a paper coating additive of the above character imparting better anti-dusting qualities to the final product than presently found in the prior art.
A further object of this invention is to provide a paper coating additive of the above character which is readily available, inexpensive, and compatible with typical paper coating colors.
Other and more specific objects will in part be obvious and will in part appear hereinafter.